Dishwasher tub gasket surface and method of making same

ABSTRACT

A relatively smooth seating surface for a gasket for a dishwasher tube formed by an expanding process is made by displacing the material forming the seating surface sufficiently from its original position established by the expanding step that the wrinkles and irregularities formed during the expanding process are merged into the smooth surface.

United States Patent 1 Long DISHWASHER TUB GASKET SURFACE AND METHOD OF MAKING SAME Inventor: Olan L. Long, Columbus, Ohio Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

Filed: May 10, 1971 Appl. No.: 141,685

U.S. Cl. ..1 13/120 M, 29/401, 72/348 Int. Cl. ..B2ld 51/18 Field of Search... ..1 13/116 F, 116 G,

113/116 H, 116 HA, 116 HH, 120 C, 120 E, 120 HA, 120 K, 120 D, 120 M, 120 DD; 72/348; 29/401; 220/74; 49/485 [451 May 15, 1973 [56] References Cited UNITED STATES PATENTS 1,979,472 11/1934 Kelley ..1 13/116 HA 2,274,835 3/1942 Koch ..1 13/120 M 3,603,035 9/1971 Kaldenberg ..49/485 Primary Examiner-Richard J. Herbst Attorney- F. H. Henson and E. C. Arenz [57] ABSTRACT A relatively smooth seating surface for a gasket for a dishwasher tube formed by an expanding process is made by displacing the material forming the seating surface sufficiently from its original position established by the expanding step that the wrinkles and irregularities formed during the expanding process are merged into the smooth surface.

2 Claims, 4 Drawing Figures DISHWASHER TUB GASKET SURFACE AND METHOD OF MAKING SAME BACKGROUND OF THE INVENTION face on the tub.

2. Description of the Prior Art Applicant is unaware of prior art dishwasher patents considered pertinent to this invention.

One known way of forming the generally right parallelepiped shape of a dishwasher tub is to use the known expanding process in which segmented dies disposed inside the tub form are moved outwardly to form the contours in the tub walls. This process also accommodates forming a gasket seating surface flange intended to be flat. However, it has been my experience that in using the expanding process to form dishwasher tubs, irregularities and wrinkling of the material forming the gasket seating surface frequently occurs. In the past, efforts have been made to flatten the surface fully by squeezing the wrinkles and irregularities out into the flat; however, even with this step it has been my experience that the irregularities and wrinkles are not adequately removed to provide satisfactory seating in all cases.

This problem of irregularities in the material occasioned by use of the expanding process is known generally in the metal working art, as evidenced, for example, in Metals Handbook 8th Edition, Volume 4, of the American Society for Metals, wherein it is stated on page 86 that The presence of gaps between the forming segments is one of the drawbacks of this method and is the reason that an alternative method, such as rubber pad forming, is sometimes selected.

SUMMARY OF THE INVENTION In accordance with my invention, a relatively smooth seating surface for a gasket on a dishwasher tub is provided by displacing the material forming that surface sufficiently from its original position established by the expanding step that the wrinkles and irregularities, to the extent they exist, are merged into the smooth surface in its displaced position. This is in contrast to the noted restriking step in the prior art in which the surface is restruck in an effort to flatten the surface to squeeze out any irregularities therein. The displacement contemplated in accordance with the invention results in a stretching of the material wherein the final contour of the seating surface is concave.

DRAWING DESCRIPTION FIG. 1 is a partly broken, schematic, side view of an expanding process arrangement by which the dishwasher tub is initially formed to its general shape;

FIG. 2 is a perspective view of the dishwasher tub as finally formed;

FIG. 3 is a perspective view of a fragment of the border of the open front face of the dishwasher tub for the purpose of illustrating in somewhat exaggerated form a character of wrinkles and irregularities which may be formed in the seating surface during the expanding process; and

FIG. 4 is a horizontal section corresponding to the line IV-lV of FIG. 2 and illustrating in somewhat exaggerated form the displaced position of the seating surface.

DESCRIPTION OF TI-IEPREFERRED EMBODIMENT The dishwasher tub has a generally right parallelepiped shape as formed and shown in FIG. 2 and includes a top wall 10, bottom wall 12, opposite side walls 14 and 16, and rear wall 18, the center portion 20 of which is absent during the expanding process and is subsequently welded to the remainder of the rear wall. The tub also includes an open front space 22 defined by the perimetric border portion generally designated 24.

During the expanding process the various embossments, ribs, and the perimetric border portion are also formed, with the exception that the rearwardly directed stub flange 26 along the outer edge of the perimetric border portion occupies the same plane as the front flange 28.

While expanding processes are well known, a schematic illustration of the arrangement for forming a dishwasher tub is shown in FIG. 1 in which the female die or backup is indicated by the numeral 30, the segmented male dies by the numeral 32, and the ram or punch press by the numeral 34. It will be appreciated that FIG. 1 is a simplified schematic and does not show the intricate configurations in the dies to accomplish forming the embossments and the perimetric border portion 24.

During the expanding process illustrated in FIG. 1 the segmented die arrangement occasions the creation of wrinkles and irregularities of a relatively minor nature in different parts of the tub. In most areas the wrinkles and irregularities, because of their minor nature, are insufficient to create any problem and in fact are generally so imperceptible that the tub must be examined relatively closely to detect these irregularities. However, it has been found that as to the seating surface to which a gasket is either attached, or against which it seats for sealing purposes, minor irregularities wrinkles can and frequently do permit leakage of water at such locations. In FIG. 3, a fragment of the perimetric border 24 is illustrated in which wrinkles 36 and irregularities 38 are shown in exaggerated size on the gasket seating surface 40 of the perimetric border portion. It is here noted that while in the illustrated embodiment the gasket is carried by the door (not shown) of the dishwasher, the problem or irregularities permitting leakage has been found to exist irrespective of whether the surface with the irregularities is that to which the gasket is attached, or is that to which the gas ket moves against and seats to effect a seal.

In accordance with the invention, the seating surface 40 the material forming the seating surface 40 is restruck in a press forming operation todisplace substantially all of the material forming the seating surface sufficiently from its original position, as established by the expanding step, that the wrinkles and irregularities are merged into a smooth contoured surface. As seen in FIG. 4, the dash line 42 indicates the original flat plane which the forward surface of the seating surface 40 occupied after the expanding step, with the restriking operation contouring the surface into the concave shape, as viewed from the front of the tub, this concave shape being shown in slightly exaggerated form in FIG. 4. In practice, as found with the segmented dies used and in which the width of the seating surface 40 is about 0.56

a contoured depth of 0.020 inches plus or minus 0.010 is sufficient to merge the wrinkles and irregularities into a smooth seating surface. It will be appreciated that the material displacing step need not result in a concave form if the original contour is convex instead of flat, and the restriking charges the contour from greater convexity to less convexity. However, the concave final contour is the currently preferred arrangement.

The restriking of the seating surface 40 to provide the contour may be accomplished in connection with the press forming step during which the flange 28 is provided at the edge of the front flange 26.

I claim as my invention:

1. ln forming a dishwasher tub including a perimetric border portion about the open face of the tub by an ex-,

panding process using a segmented die which tends to create wrinkles and irregularities in said perimetric border portion, the method of providing a relatively smooth seating surface for a gasket in said perimetric border portion comprising displacing the material forming said seating surface sufficiently from its original position established by said expanding step that said wrinkles and irregularities are merged into said smooth surface.

2. In forming a dishwasher tub including a perimetric border portion about the open face of the tub, by an expanding process using segmented dies which tend to create wrinkles and irregularities in various portions of said tub including said perimetric border portion, the method of providing a relatively smooth seating surface for a gasket in said perimetric border portion comprising restriking said seating surface to sufficiently displace the material of said seating surface and for a sufficient part of its width to place a transversely curved contour therein sufficiently out of the original plane of said seatingsurface that said irregularities created by said expanding process are merged into said smooth contoured surface. 

1. In forming a dishwasher tub including a perimetric border portion about the open face of the tub by an expanding process using a segmented die which tends to create wrinkles and irregularities in said perimetric border portion, the method of providing a relatively smooth seating surface for a gasket in said perimetric border portion comprising displacing the material forming said seating surface sufficiently from its original position established by said expanding step that said wrinkles and irregularities are merged into said smooth surface.
 2. In forming a dishwasher tub including a perimetric border portion about the open face of the tub, by an expanding process using segmented dies which tend to create wrinkles and irregularities in various portions of said tub including said perimetric border portion, the method of providing a relatively smooth seating surface for a gasket in said perimetric border portion comprising restriking said seating surface to sufficiently displace the material of said seating surface and for a sufficient part of its width to place a transversely curved contour therein sufficiently out of the original plane of said seating surface that said irregularities created by said expanding process are merged into said smooth contoured surface. 